Numerous situations exist in which a body cavity needs to be catheterized to achieve a desired medical goal. One relatively common situation is to provide nutritional solutions or medicines directly into the stomach or intestines. A stoma is formed in the stomach or intestinal wall and a catheter is placed through the stoma. This surgical opening and/or the procedure to create the opening is common referred to as “gastrostomy”. Feeding solutions can be injected through the catheter to provide nutrients directly to the stomach or intestines (known as enteral feeding). A variety of different catheters intended for enteral feeding have been developed over the years, including some having a “low profile” relative to the portion of the catheter which sits on a patient's skin, as well as those having the more traditional or non-low profile configuration. These percutaneous transport catheters or tubes are frequently referred to as “gastrostomy tubes”, “percutaneous gastrostomy catheters”, “PEG tubes” or “enteral feeding catheters”.
To prevent the PEG tube from being pulled out of the stomach/intestinal wall, various types of retainers are used at a distal end of the catheter. Examples of conventional devices with Malecot tips or similar expanding tips are found at, for example, U.S. Pat. No. 3,915,171 for “Gastrostomy Tube” issued to Shermeta; U.S. Pat. No. 4,315,513 for “Gastrostomy and Other Percutaneous Transport Tubes” issued to Nawash et al.; U.S. Pat. No. 4,944,732 for “Gastrostomy Port” issued to Russo; and U.S. Pat. No. 5,484,420 for “Retention Bolsters for Percutaneous Catheters” issued to Russo. Exemplary commercial products include the Passport® Low Profile Gastrostomy Device available from Cook Medical, Inc. of Bloomington, Ind. and the Mini One™ Non-Balloon Button available from Applied Medical Technology, Inc. of Brecksville, Ohio. A shortcoming of these devices relates to the manner of insertion and withdrawal of a catheter or tube incorporating these retaining fixtures (e.g., a gastrostomy tube) into a body lumen such as into the stomach.
Balloons can be used in place of these conventional devices with Malecot tips or similar expanding tips. A balloon, typically made of a “soft” or elastomeric medical grade silicone, is attached to the end of the catheter and is deflated for insertion through the stoma and then inflated to hold the enteral feeding assembly in position. While these balloons have many advantages, balloons may eventually leak and deflate. In addition, “soft” or elastomeric medical grade silicone has a tendency to “creep” or stress relax over time which can change the dimensions of the balloon.
Various types of medical devices incorporating inflatable balloons devices are known and widely used in the medical field. For example, endotracheal tubes and tracheostomy tubes utilize inflatable balloons to create a seal that prevents the passage of mucus into the lungs. Pilot balloons, pressure gauges, and inflation indicators are used to provide a continuous reading of the pressure in the balloon in these devices. That is, these devices provide an output that conveys continuous or uninterrupted information showing pressure increases and decreases in the balloon. These devices are described at, for example, U.S. Pat. No. 3,642,005 for “Endotracheal Tube With Inflatable Cuff” issued to McGinnis; U.S. Pat. No. 4,266,550 for “Pressure Indicators For Inflatable Cuff-Type Catheters” issued to Bruner; U.S. Pat. No. 6,732,734 for “Pilot Balloon For Balloon Catheters” issued to Ogushi et al.; and U.S. Pat. No. 7,404,329 for “Pressure Gauge For Use With An Airway Lumen” issued to Quinn et al.
In addition to pilot balloons, pressure indicators incorporating bellows or diaphragms are known and electronic pressure indicators are known. For example, a simple bellows pressure indicator for showing continuous reading of fluid pressure is described in U.S. Pat. No. 3,780,693 for “Visible Fluid Pressure Indicator” to Parr. U.S. Pat. No. 7,383,736 “Device and Method for Pressure Indication” issued to Esnouf, describes a bellows device for use with a laryngeal mask balloon or other airway management equipment incorporating balloons. The device of Esnouf incorporates a bellows that is displaced by a differential pressure between the outside of the bellows and the inside of the bellows to provide a continuous reading of the increases and decreases in the pressure of fluid in the balloon. U.S. Pat. No. 7,018,359 for “Inner Pressure Indicator of Cuff” issued to Igarashi et al., describes a bellows or spring structure for use with a tracheostomy tube balloon or endotracheal tube. The device of Igarashi et al. is connected to the balloon through an inflation tube and has an inflation valve at the other end that is connected to a syringe. The device uses a bellows and/or spring indicator provide a continuous reading and display of the increase and decrease in the pressure of fluid in the balloon through movement of the bellows against a numerical scale printed on the housing. U.S. Pat. No. 5,218,970 for “Tracheal Tube Cuff Pressure Monitor” issued to Turnbull et al. describes a continuous pressure monitor for a tracheal tube incorporating an electronic pressure sensor such as a silicon strain gauge pressure sensor, a processor that performs various calibration, scaling and calculation operations on the signal from the sensor and provides an output to a numeric display conveying a continuous reading of the increases and decreases in the pressure of fluid in the balloon.
These indicators are adapted for airway devices where careful and constant monitoring of balloon pressure is important. In order to adequately seal the space between the lumen of the trachea and the balloon, there is a tendency to overinflate the balloon, which may result in tissue damage. If the pressure is too low, the balloon does not adequately seal the space between the lumen of the trachea and the balloon thereby allowing secretions to enter the lungs causing pneumonia and other respiratory complications. In order to provide careful control of the balloon pressure, these pilot balloons, bellows and diaphragm indicators and electronic sensors are designed to convey a continuous reading of the increases and decreases in the pressure of fluid in the balloon.
While this level of sensitivity and continuous reading is desirable, pilot balloons and similar bellows or diaphragm indicators are relatively large and typically require skill and experience to accurately interpret the output of these conventional devices as they provide a continuous reading of pressure. While electronic pressure sensors are accurate and are generally easy to read, they are relatively large and expensive. Scaling these types of devices down to a sufficiently small size so they can be used with a low-profile PEG tube only highlights the problems associated with the size, calibration, accuracy, and reading or interpreting the output of these devices.
U.S. Pat. No. 6,878,130 for “External Inflation Indicator for a Low Profile Gastrostomy Tube” issued to Fournie et al. describes an external inflationary indicator similar to a pilot balloon integrated into the base of a gastrostomy device having a retainer balloon. The device of Fournie et al. provides a continuous tactile reading of the inflationary state of the retainer balloon. The Fournie et al. device utilizes two generally bubble-like portions that assume a generally convex shape when the retainer balloon is inflated and a generally concave shape when the balloon is deflated. The changing shape of these generally bubble-like portions provides a continuous tactile indication or reading of the inflationary state of the balloon. In addition, the external inflationary indicator provides continuous visual indication of the inflationary state of the retainer balloon through the use of a separating bar dividing these two generally bubble-like portions of the indicator. The separating bar visually separates as the balloon becomes fully inflated to indicate the inflationary state.
The device of Fournie et al. is relatively complicated and adds significantly to the manufacturing process and costs. In addition, the indicator increases the overall profile (i.e., shape, height, etc.) of the head, which is generally undesirable to the user. In addition, the use of moving, mechanical indicator components is always prone to failure or malfunction of such components, which results in a complex medical procedure to replace the device.
Accordingly, there is a need for a relatively simple yet reliable pressure change indicator that can be readily integrated into the head of a PEG tube without unduly increasing the size or mechanical complexity of the head, and which is easy to view externally.